Radio frequency identification (RFID) is a technology whereby specific targets can be identified, and related data can be read and written, via radio frequency (RF) signals. Thanks to the RFID technology, an RFID tag can be provided on the package bag of an article, so as for a reader within a predetermined distance from the article to obtain the data (e.g., the year of manufacture, the expiration date, etc.) stored in the RFID tag. Compared with barcode technology, RFID not only features a larger storage capacity, but also is more convenient to use, for there is no need to establish mechanical or optical contact with RFID tags. Hence, RFID has been extensively used in preventive measures for counterfeit banknotes, verification mechanisms for identification cards, electronic fare collection systems, and electronic pedigrees, to name only a few examples. Today, RFID is as ubiquitous as important in people's daily lives.
RFID tags can be divided, according to their sources of energy, into three categories: passive, semi-passive, and active. Take the most common passive RFID tags nowadays for instance. The passive RFID tag 1 shown in FIG. 1 is composed of a substrate 11, a transceiver antenna 12, and a chip 13. The substrate 11 is typically made of polyimide. The transceiver antenna 12 is formed on the substrate 11 by an etching process, which generally includes attaching a copper foil to the substrate 11 and etching the copper foil according to a predesigned antenna configuration in order to form the transceiver antenna 12. The chip 13 has two ends respectively connected to the feed-in ends of the transceiver antenna 12. When a reader within a predetermined distance from the RFID tag 1 sends out an RF signal, the transceiver antenna 12 can, after receiving the signal, transmit the data stored in the chip 13 to the reader using energy generated from electromagnetic induction.
Referring to FIG. 1, the RFID tag 1 depends on the transceiver antenna 12 to receive and transmit RF signals and thereby drive the chip 13 in the tag to execute the corresponding procedures. When attached to a non-conductive article (e.g., a plastic package bag, paper, wood, etc.), the RFID tag 1 can perform signal transmission wherever possible, exchanging information with a reader within a predetermined distance. When the RFID tag 1 is attached to the surface of a metal article, however, the metal article will, according to the image theory, generate image pulses which are in antiphase, and hence destructively interfere, with the RF signals transmitted by the transceiver antenna 12. Once the RF signals are destroyed and rendered undeliverable to the reader, the reader will have problem reading the information in the RFID tag 1. Destructive interference refers to a phenomenon in which a peak of a wave and a valley of another wave arrive at the same point, and in which therefore the amplitude of the resultant wave is smaller than the amplitude of each of the component waves. If the amplitude of a wave completely cancels the amplitude of a destructively interfering wave, complete destructive interference takes place.
In today's logistics systems, it is common practice to package a to-be-delivered article in a package bag with a metal lining in order to keep the article dry, or prevent the article from rusting or growing mold, or protect the article from deterioration which may otherwise result from exposure to light. The most common example of such package bags is the electroplated aluminum foil bag, whose interior is electroplated with an aluminum foil. However, as stated above, the image pulse problem arises when the RFID tag 1 is provided on a packaging material with a metal lining. More particularly, attaching the RFID tag 1 to an electroplated aluminum foil bag will seriously compromise the readability of the RFID tag 1 or even reduce the read distance of the tag to approximately 0 meter, in which case the RFID tag 1 is practically unreadable. Furthermore, electroplated aluminum foil bags are typically used to package articles of relatively small sizes and relatively short shelf lives, but it is difficult to design inexpensive and compact RFID tags for use on electroplated aluminum foil bags without impairing the low-cost and small-size features of the bags. The lack of RFID tags suitable for use with electroplated aluminum foil bags adds to the inconvenience of logistics management.
Therefore, the issue to be addressed by the present invention is to improve the conventional package bags so that a package bag not only can have a moisture-proof and reflective metal layer, but also can be provided with an RFID tag to facilitate logistics management.